Zheng Baobing, Zhang Meiguang, Wang Canjun
College of Physics and Optoelectronics Technology, Nonlinear Research Institute, Baoji University of Arts and Sciences, Baoji 721016, China.
Materials (Basel). 2017 Feb 4;10(2):128. doi: 10.3390/ma10020128.
First-principles calculations were employed to study the mechanical properties for the recently proposed tetragonal B₄CO₄ (-B₄CO₄). The calculated structural parameters and elastic constants of -B₄CO₄ are in excellent agreement with the previous results, indicating the reliability of the present calculations. The directional dependences of the Young's modulus and shear modulus for -B₄CO₄ are deduced in detail, and the corresponding results suggest that the -B₄CO₄ possesses a high degree of anisotropy. Based on the strain-stress method, the ideal tensile and shear strengths along the principal crystal directions are calculated, and the obtained results indicate that the shear mode along (001)[100] slip system dominates the plastic deformation of -B₄CO₄, which can be ascribed to the breaking of the ionic B-O bonds. The weakest ideal shear strength of 27.5 GPa demonstrates that the -B₄CO₄ compound is not a superhard material, but is indeed a hard material. Based on the atomic explanation that the ternary B-C-O compounds cannot acquire high ideal strength, we propose two possible routes to design superhard B-C-O compounds.
采用第一性原理计算方法研究了最近提出的四方相B₄CO₄（-B₄CO₄）的力学性能。计算得到的-B₄CO₄的结构参数和弹性常数与先前的结果非常吻合，表明当前计算结果的可靠性。详细推导了-B₄CO₄的杨氏模量和剪切模量的方向依赖性，相应结果表明-B₄CO₄具有高度的各向异性。基于应变-应力方法，计算了沿主晶向的理想拉伸强度和剪切强度，所得结果表明沿(001)[100]滑移系的剪切模式主导了-B₄CO₄的塑性变形，这可归因于离子型B-O键的断裂。27.5 GPa的最弱理想剪切强度表明-B₄CO₄化合物不是超硬材料，但确实是一种硬质材料。基于三元B-C-O化合物无法获得高理想强度的原子解释，我们提出了两种设计超硬B-C-O化合物的可能途径。
